The present invention relates to a power source device for an ink jet printer which is of the type having a plurality of separate deflection electrodes and, more particularly, to one capable of supplying the respective deflection electrodes with voltages which are so controlled as to eliminate discharging across the separated deflection electrodes.
In a charge and deflection type ink jet printer, ink supplied to a head is ejected from a nozzle of the head to be separated into a drop at a predetermined position. A charging electrode is located at the position where the separation of the ink into a drop occurs and supplied with charging voltages to selectively charge the drops. The charged drops are deflected by a deflection electrode to impinge on a paper laid on a platen so as to print out characters and/or figures thereon. The other drops left uncharged by the charging electrode are collected by a gutter.
In an ink jet printer having such a construction, as the distance from the nozzle of the head to the recording surface on the platen increases, the influence of Coulomb force acting between adjacent drops, air resistance and the like becomes significant to cause distortions in the printed characters and pictures. While the distortions may be eliminated by reducing the distance between the nozzle of the head and the recording surface on the platen, such cannot be implemented unless a higher deflection voltage is applied across the deflection electrode. The higher deflection voltage, however, enhances the tendency toward distortions in deflection and leaks at the deflection electrode.
To solve the problem discussed above, there has been proposed and put to practical use a charge and deflection type ink jet printer in which the deflection electrode is divided into a plurality of deflection electrodes, such as two, and different deflection voltages are applied to the respective deflection electrodes. This type of ink jet printer furnished with two separate deflection electrodes is capable of suppressing distortions in deflection and, additionally, setting up considerable amounts of deflection.
However, the ink jet printer with two deflection electrodes requires at least two high-tension power source sets which proportionally add to the cost. Moreover, if the two deflection voltages do not build up or down equally to each other, the voltage across the deflection electrodes will be increased to invite a leak or, in the worst case, discharging. Such would damage other circuitries installed in the printer and/or entail malfunctions thereof.